1. Field of the Invention
This invention generally relates to a exhaust gas processing device of vehicles, and more particularly, to a holding sealer used for the exhaust gas processing device.
2. Description of the Related Art
The number of cars is greatly increasing since the beginning of this century, and the amount of exhaust gas from car's engine room have been increasing amazingly as increasing the number of cars. Especially, various materials in the exhaust gas from diesel engine trigger environmental pollution, so that these materials have been influencing seriously on global environment currently.
Under this circumstance, various exhaust gas processing devices have been suggested, and these have been used practically. Typical exhaust gas processing device has a casing (metallic shell) on a exhaust pipe connected to a exhaust gas manifold of the engine room, in which casing, a exhaust gas processing body having lots of small holes is arranged thereon. As an example of the exhaust gas processing body, there are a catalyst carrier and a diesel particulate filter (DPF). For example, in the case of DPF, particles are trapped by walls around holes during the exhaust gas passing through the exhaust gas processing body based on the above structure, thereby particles can be removed from the exhaust gas. Constitution materials of the exhaust gas processing body are metals, alloys, and ceramics, etc. As typical example of the exhaust gas processing body comprising ceramics, a honeycomb filter made by cordierite is known. Recently, from the viewpoint of the heat resistance, a mechanical strength, chemical stability and etc, a porous silundum sintering body is used as the exhaust gas processing body.
Usually, the holding sealer is placed between the above exhaust gas processing body and the metallic shell. The holding sealer is used for protecting a breakage due to a contact of the exhaust gas processing body with the metallic shell during vehicle runs, and for protecting a leakage of the exhaust gas from a gap between the metallic shell and the exhaust gas processing body. Also, the holding sealer plays an important role for preventing the exhaust gas processing body from falling off due to an exhaust pressure of the exhaust gas. Moreover, the exhaust gas processing body needs to keep high temperature for stabilizing the reaction, and also the holding sealer needs the heat resistance. As a constitutional member satisfying these requirements, there is a sheet member including inorganic fibers such as alumina system fiber, etc.
The sheet member has wound around at least a portion of an outer surface except an open surface of the exhaust gas processing body, and the sheet member functions as the holding sealer by fixing as one body with the exhaust gas processing body by means of taping. Then, the one whole body is assembled into the exhaust gas processing device by pressing into the metallic shell.
It is difficult to handle conventional sheet member because the usual sheet member is bulky and fibers are scattered during a cutting process. Therefore, several methods are proposed in order to improve the handling of the sheet member when used as the holding sealer of the exhaust gas processing device. For example, one method is suggested that the sheet member including inorganic fibers is processed as so-called needling process, inorganic fibers are inter-woven along with a direction of a thickness of the sheet member, the sheet member having a large amount of volume is compressed and is to be thinner. (For example, see JP-A 7-286514)